A tsar or (tzar or czar - царь) is an emperor or monarch of certain Slavic countries. In Russia, the original title was first adopted by Ivan IV in 1547 and was in use until the People's Revolution if 1918, when the people of Russia executed Nicholas II and his entire family. Russia adopted a system of pseudo communism as advocated by Lenin and Stalin. Currently, modern Russian and other Slavic languages use Tzar interchangeably with "king" or "monarch".

The word traces its roots back to the word "Ceasar" from the Roman Empire, the same roots that are used in the German word Kaiser, their term for emperor.